linux-kernel - RE: [PATCH V3 2/4] drivers/i2c/busses/i2c-at91.c: add new driver

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Message-ID: <EF2E73589CA71846A15D0B2CDF79505D087B3C9440@wm021.weinmann.com>
Date:	Wed, 9 Nov 2011 17:01:07 +0100
From:	"Voss, Nikolaus" <N.Voss@...nmann.de>
To:	"'Ryan Mallon'" <rmallon@...il.com>
CC:	"'linux-i2c@...r.kernel.org'" <linux-i2c@...r.kernel.org>,
	"'linux-arm-kernel@...ts.infradead.org'" 
	<linux-arm-kernel@...ts.infradead.org>,
	"'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>,
	"'ben-linux@...ff.org'" <ben-linux@...ff.org>,
	"'khali@...ux-fr.org'" <khali@...ux-fr.org>,
	"'nicolas.ferre@...el.com'" <nicolas.ferre@...el.com>,
	"'balbi@...com'" <balbi@...com>
Subject: RE: [PATCH V3 2/4] drivers/i2c/busses/i2c-at91.c: add new driver

Hi Ryan,

> > +#include <mach/at91_twi.h>
> 
> 
> This include file looks like it only contains register definitions which
> are used in this file. Would be good to either move them directly into
> this driver or move the header file to this directory and make it a
> local include.

Ok.

> > +
> > +	dev->dev = get_device(&pdev->dev);
> 
> 
> Is this (and the put_device(&pdev->dev) in the exit code) necessary? I
> see that some other i2c drivers do this also, but I'm not familiar with
> using it in other device drivers. Isn't the reference count for
> pdev->dev already incremented by the fact we are probing the device?

It is incremented by the platform_device_register() which does a
device_add(). This seems to be enough, I removed the get-/put_device().


> 
> > +	dev->irq = irq->start;
> > +	platform_set_drvdata(pdev, dev);
> > +
> > +	dev->clk = clk_get(&pdev->dev, "twi_clk");
> 
> 
> This didn't get answered. Can't you just do:
> 
> 	dev->clk = clk_get(&pdev->dev, NULL);
> 
> and clkdev should figure out the correct clock based on the device pointer?

No, this doesn't work on at91 since the clocks have no dev_id property
but only con_id. I cannot see a reason for this, but that's the way it's
done. Multiple hardware interfaces are handled via a lookup table.


> > +	rc = i2c_del_adapter(&dev->adapter);
> 
> 
> Most of the other i2c drivers don't check the return code for
> i2c_del_adapter. If this fails then you will unload the module, but
> potentially leak resources that i2c_del_adapter failed to free up. Not
> sure what the correct answer is here.

I don't really check the value but use it has exit code for the remove()-
function to indicate something went wrong. Just ignoring it wouldn't heal
the resource leakage.

Thanks for reviewing,

Niko


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